S. M. Dohanian.
Preliminary Experiments for the Control of Certain European Vine Moths by Fumigating with Cyanogas Calcium Cyanide.
Psyche 34:146-156, 1927.

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146 Psyche [June-August
PRELIMINARY EXPERIMENTS FOR THE CONTROL OF CERTAIN EUROPEAN VINE-MOTHS BY FUMI-
G-4TING WITH CYANOGAS CALCIUM
CYANIDE.1
BY S. M, DOHAMAN,
Somerville, Massachusetts.
In western Europe there is no fruit cultivated as extensively as the grape.
Travelers there are at once imprmsed by its general culture. Vineyards are exceedingly common in Portugal, Spain, Italy) Francel Switzerland and western Germany, the parts of Europe with which the writer is fandiar. It is natural, of course, to assume that a plant as common as the grapevine must have a large number of insect enemies. And it has. There are more than a dozen insects which may be considered of economic importance. The most notorious of them alll however, are two small Tortricidsl commonly known in Europe as Co- chylis (Clysia ambiguella Hb.) and Eudemis (Polychrosis botrana Schiff .).
Records show that for more than two centuries these two pests-and they are pests in the full significance of the word- have been present in the vineyards of Europe. Over a period of many years the annual loss to the vineyardists in each of the countries mentioned above has been millions of dollars. Owing to this enormous damage they have been the subjects of study by various noted entomologists in these countries, but till now no effective method of control has been discovered. The investigations of the wrfier in the winter of 1925-26 .
brought forth the interesting information that thse two in- sects are unable to survive a dry season. While he was in Spain during the spring and summer of 1924 he was witness to a severe drought lasting from mid-April to late that autumn. This dry spell had reduced their numbers more than 95% for the season of 1925. The month of Januaryl 1926, was spent in an exhaustive 1 In November, 1925, the American Cyanamid Sales Co. of New York,
sent the writer, who was then in their employ, to Europe to investigate the possibilities of Cyanogas calcium cyanide being used for the control of the vine pests mentioned in this article.




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19271 Control of European Vine-moths 147 survey of the country for an infestation where methods of control with calcium cyanide could be studied) but withoutsuccess, for the infestations throughout the country had been reduced to a minimum.
European entomologists have uncovered a formidable array of natural enemies during their constant studies of these two pests. There are recorded some forty hymenopterous parasites of the eggs) larvq and pup= common to both pests. Theyare also frequent victims of several fungi and bacterial diseases. The annual loss occasioned by the two pests) despite these natural enemies) has always been enormous) for which reason many efforts at artificial control have been attempted. One of the most promising artificial control measures was that attempted on a small scale by Dr. Friedrich Stellwaag of Neustadt a/d Haardt) Germany) in 1917-1918.2 He conceived the idea of fumigating the vines with ECN gas by the use of sodium cyanide and sulphuric acid under cover) because of the success this method had produced in the California citrus groves. His prelj-minary experiments, well planned and tjhoroughly ex- ecuted, were carried on between April 24 and June 12) 1917. In April the fumigations were made on the leafless vine stalks (winter condikion) and in June they were fumigated in their summer condition. The results obtained in Dr. Stellwaag7s ex- periments may be briefly summarized as follows : 1. Fumigation of the plants in their leafy (summer) condition) even. when only small quantities of the gas are used, cause damage to the foliage without completely killing the pests.
2. On the other hand the
vines in their leafless (winter) condition are able to withstand larger quantities of the gas, sufficient (under the conditions of the experiment) to kill the cocoons found under the tent in which the fumigation was done.
The results of his 1918 tests3 checked substantially with those of the previous year, except that more injury to the vines was noted due to rapid formation of the gas. Furthermore, Dr. Stellwaag believed that this form of fumigation was ''tloo fussy, 2"Der Weinbau der Rheinpfalz," No. 8, August 1917. 3"Der Weinbau der meinpfalzl" No. 1, Januaryl 1919.



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148 Psgche [June- August
too expensive and unreliable.)' Therefore he discontinued fur- ther experimenting along these lines.
With the development of calcium cyanide during recent years, it was believed that these objections were eliminated. It is a product convenient to handle) easy to apply, les danger- ous) and much more economical. Its greatest asset, how-ever) is that the gas is not evolved suddenly and turbulently. When normal dosages are applied the chance of injury to living plant tissues is at a minimum) for the gas evolves gradually) the peak being reached some little time after the plant tissues have re- ceived small amounts of the gas produced soon after applica- tion. In the firm belief that calcium cyanide would succeed where the old process of sodium cyanide plus sulphuric acid had failed, the writer was sent to Europe in December, 1925, to investigate the possibility of control of Eudemis and Cochylis with Cyanogas calcium cyanide.
As mentioned above, no adequate location could be found in Spain) due to the scarcity of the pests in that country. How- ever) two suitable sites were found; the first being near Bordeaux, France, the other in Lausanne7 Switzerland. Dr. J. Feytaud7 director of the Station Entomologique de Bordeaux, very kindly co-operated in the undertaking by allowing the use of his lab- oratory facilities and also permitting us to experiment in vine- yards under his charge. Similarly, Dr. H. Faes) director of the Station Fkdhrale dJEssais \Titicoles de Lausanne, courteously ex- tended the use of laboratory and vineyards, Both thus faci- litated the experimental work.
Life Histories of the Pests.
Before proceeding with the details of the experiments it is well to mention briefly the salient features in the life histories of these insects. Essentially they are alike, the only variation being that Clysia arnbiguella (Cochylis) has two annual genera- tions) whereas Polychrosis botrana (Eudemis) has sometimes a partial and sometlimes a full third generation. Both insects pass the winter as pup% within rather thick cocoons spun by the larvz. The cocoons are ordinarily attached to the vine stalks) although at times they have been found on rocks, fences) the



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19271 Control of European Vine-moths 149 wooden supports placed beside the stalks, and other similar objects. In seeking locations for hibernation the fullgrown larvz instinctively select such sheltered and secluded spots, in. which to spin their cocoons, as will insure complete protection against the elements during the long hibernating period. Con- sequently the cocoons are to be found in the folds of the bark, in crevices, holes, fissures) cracks) etc. The newly formed co- coons of Eudemis are clean and snow-white; whereas those of Cochylis are invariably covered with dirt) dust and debris of all sorts) making them difficult of detection. The adult moths emerge late in April or early May, simul- taneous with the bursting of the buds, and are present thexe- after until early in the fall. The Cochylis adults are nocturnal in habit) while those of Eudemis are more active at dawn and at dusk of day. The females, after fertilization, commence laying their tiny and solitary eggs in the flowers of the host plant. These eggs hatch in from 7 to 30 days. The larv~ of the first generation attack and destroy the flowers, while those of the following generations damage the fruits. The second genera- tion adults of Eudemis appear about the third week of June (a cycle of 7 weeks) while those of Cochylis do so towards the middle of July (a cycle of 9 weeks). Thus it will be seen that from early May until cool weather stops their activities (late September) all four stages of these insects may be found in the field.
The Experiments
The aggregate damage caused annually by these insects is enormous. The idea was also gathered from entomologists in- terviewed that no difficulty would be experienced in locating heavy infestations. In view of these facts it was the original intention to experiment with Cyanogas calcium cyanide for the control of the pests by treating the infested vines without dis- turbing or removing the insects from their natural hibernating quarters. However) when the actual work was begun the plans were changed to suit the work to existing conditions. Bushels of bark were peeled off the vines in a number of infested vineyards within close proximity of the two laboratories) and all cocoons of



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160 Psyche [June-August
the two pests were then removed from them in the laboratories. In detaching them from the bark many of the cocoons tore open, for they were attached very firmly. About 700 cocoons of the two species were recovered from about twelve bushels of peeled bark.
For their treatment with calcium cyanide, the insects (cocoons) were retained in a coarse muslin suspended on the stalks fumigated. No pup% were used in the experiment which failed to respond to a gentle pinch with the forceps, prior to fumigation.
The vines.-The vines treated in Switzerland were of a species called "chasselas," indigenous to that country, while in B'rance vines with American rootstock were selected. Vines of varying ages, from 5 years to 50 years, were treated in order to secure information concerning the resistance of plants of varying ages to the action of HCN gas.
In Switzerland the majority of vineyards are of the type where the vines are grom7n singly, trained on wooden supports about 1 meter or a little over in height, placed in the ground close to the pruned vine just as soon as growth begins in the spring. The French methods of cultivation are of three types: (11, individual vines (as in Switzerland) pruned close to the ground; (21, vines trained on a single line of wire stretched the full length of each row; and (3), taller vines trained ondouble lines of wire, the first line about 30-35 c. m. above the ground,
and the second wire about an equal distance above the first. The wires are attached to strong wooden posts in the rows, placed about 12-15 meters apart. The majority of vineyards in France are of the third type.
The covering.-The protection afforded the insects by their heavy covering (the cocoons) and also the fact that their res- piratory system is at the minimum period of functioning during this season of the year (late winter and early spring) and stage ~f their life, made it at once evident that open air fumigation would be futile. Consequently a canvas tent and a cylindrical galvanized iron can were used in covering the vines for the treatments. The tent, of heavy impermeable canvas, was made large enough to permit treatment of' four vines together. Its



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19271 Control of European Vine-moths 151 dimensions were 1.25 m. x 1.25 m. x 0.65 m. On its four sides
a flap 12 c.m. wide was planned to insure against leakage of gas during fumigations, by placing earth or stones or other weighty materials on the flaps. The galvanized iron can was 95 cm. high with a diameter of 60 c.m. The galvanized iron can was originally thought of because of the certainty of its being airtight and rain proof, very important considerations for overnight fumigations. It has the further advantage in winter fumigation work over the canvas tent in that the temperature within it rises several degrees above that of the outside air. Tests made to determine this point showed an increase of 2 degrees C. after an exposure of one hour, when the outside temperature was 10 degrees C. and an increase of 5 degrees C. after an exposure of two hours with the outside temperature at 16 degrees C. Dosages and exposures.-The cubic content of t'he tent was 940 litres. In order to secure a concentration of HCN gas equal to 1% of the volume of the space within this tent, it was cal- culated that approximately 45 grams of Ca (CN)2 should be ap- plied. For a dosage of 10% volume, therefore, it would be necessary to use ten times 45 grams, or 450 grams. Likewise it was found that 12.5 grams of Ca (CN)2 would produce a 1% volume concentration of HCN gas when applied under the gal- vanized iron can, the cubic content of which was 270 liters. The dosages used in the 71 experiments varied from 0.275% volume to 10.00% volume, each dosage being tried at least twice with a given exposure. The exposures were varied also, these being dependent on the dosages. The exposures were for periods of 30 minutes, 45 minutes, 1, I;, 2, 2$ and 3 hours. Some overnight exposures were also tried. In general, smaller dosages were used in the long exposures and larger dosages in exposures of short periods.
The treatments.-Dr. Stellwaag, in the experiments referred to above, found that the grapevine is an extremely delicate and tender plant and that it is unable to withstand heavy concen- trations of HCN gas. In view of this, coupled with the desire to cause as little injury as possible to the plants, the dosages used in the first twenty experiments were less than 1% volume. Beginning with a dosage of 0.275% volume, with an exposure



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152 Psyche [ June-August
of 30 minutes, both dosage and exposure were increased to 1% volume and treated one hour, but witn no appreciable effect on the insects or on the plants. Gradually the dosages were in- creased even beyond that fatal to the insects up to 10% volume to note the effect of abnormally strong applications of HCN gas on the vines. It is interesting to note that even such a heavy dosage as 10% volume (450 grams to a space of 940 liters) just before the flow of sap had commenced (on March 25, 1926) did not prove fatal to the plants, merely "retarded growth" being the observation made on the following 12th of April. In all the experiments fresh Cyanogas calcium cyanide grade "A" dust was used. The exact dosage of the dust, after being measured on balance scales, was placed in a foot-pump duster and applied under the tent or galvanized iron can. No difference was noted in the results when the nozzle of the duster was directed to the bottom of the covering or to its top. In the latter case the plants would be covered with a fine coating of the dust, whereas when the dust was directed to the ground there would be practically no dust on the vines. In either case the effect both on the insects and the plants treated was the same. To discuss each of the 71 experiments in detail seems un- necessary, for the majority resulted in only partial kills or no kills at all. Only in nine of the experiments was complete kill of the insects exposed to treatment secured, the details of which are given in the accompanying table.
The primary object of Experiments 29, 30, 31 and 32 was to see if abnormally excessive dosages, during exposures of 30 and 45 minutes, under the tent and also under the galvanized iron can, would be fatal to the vines. Observations on the condition of the plants made on April 12, a short while after the leaf buds had burst, showed them to be slightly retarded in growth. No injury was caused to any of the plants in their dormant con- dition even with such strong applications of the poison. Experiment 53 was conducted on a fair, warm and calm afternoon. 15 naked pupae were exposed to 3.5% volume (45 grams of poison to 270 liters of space) for one hour, from 2 :I5 to 3:15 p. m., under the galvanized iron can. The nozzle of the



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Exp. Number
-
-
Date
---+-----
Hour4
---------
Sun
--------
Clouds
-------
Wind
Temperatures
Relative Humidity5
--
Exposure
--
Dosage
-----
Rate
-------
No pupae treated
--- -
% pupae killed
Effect on vines
--------
Covering
30
3-25
----
3:15 P.M.
29
--
3-25
----
3 :03 P.M .
----
Yes
. No
Weak
--
54O F.
59 %
---
45 min.
----
450 gr.
--
10% vol.
----
10
--
100%
retarded
growth
--
Tent
55
4-5
---
3:23 P.M.2:30
Yes
No
gentle
--
63OF.
54%
3 hrs.
25 gr.
2%vol.
--
11
100%
4-5
--
3:15 P.M. 3:59 P.M.
I
57
-----
--
4-6
P.M.4:33
Yes
---------
No
--------
calm
61å¡F
----
51%
-------
2 hrs.
-----
32 gr.
2.5%vol.
5
------
100%
I----
i:08 P.M.
59
4-6
--
P.M.
Yes
No
calm
--
64OF.
47%
1; hrs.
38 gr.
-----
3%vol.
--
6
100%
7:32 A.M.
Yes
Hazy Yes
partial partial
light
Weak
slight slight calm
45 min.
30 min.
450 gr.
--
10% vol.
--
10
100%
---
none
30 min.
--
125 gr.
p-
10% vol.
10
100 %
much
retarded
45 min.
225 gr.
1 hr.
45 gr.
--
3.5% vol.
--
15
--
100%
---
a little
retarded
125 gr.
10% vol.
p-
10
100%
--
growth
retarded
none 1 none 1 none
----------
G. I. Can.G. I. Can.G. I. Can. G. I. Can. Tent G. I. Can. Tent G. I. Can.
^Beginning of treatment.
6Af start pf fumigation,




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154 Psyche [J une-August
foot-pump duster was directed upward, and at the termination